Can anybody advise about the best course of action? I have a combi boiler that has its flue exhaust going out through the wall, but it appears that over time, the steam from the flue has had a damping effect on the external wall over a stretch of a good few metres above the exhaust. The paint has started to flake away, but most importantly, it looks like some of the moisture collects under an exterior windowsill about 3-4m above the exhaust, and this has eventually become a problem at this location, in that the damp has crept through to the interior wall, giving us a damp patch under the window on the inside. Although it is only a small damp patch at the moment, I am thinking it would be best to try and get a new flue exhaust, or better still just a new terminal guard, that might include a solid upper surface that would act as some sort of directional 'hood', to push the steam exhaust further away from the wall before it can rise upwards.
I have a feeling this would go a long way to sorting out the problem - I don't think it is rising damp in the normal sense, the wall beneath the boiler seems to be fine, and there seems to already be an additional damp proofing membrane in the wall above the exhaust at a height of about 2m, which doesn't seem to be preventing the problem, which would be consistent with the theory that it is moisture settling on the wall from the steam. Maybe this is just another sort of membrane though, I don't know enough about damp proof coursing to know exactly what it is.
Does anybody know where I could get a new terminal guard with some sort of directional hood that would help with this problem, and also, if there is any useful anti damp product that can be applied from outside to try and reduce the existing damage?
Thanks very much for any suggestions.
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